(1) Field Of The Invention
This invention generally relates to novel improvements in movable supports for machinery or mechanisms of diverse character and especially relates to new and novel improvements in supports for motors and machines which are adapted to be powered by motors.
(2) Description Of The Prior Art
Supports of the general type indicated above are well known in the art and, having regard particularly to supports for motors or articles of machinery, prior art examples will be given in the following.
Before referring to specific prior art patents, it is well to understand that the present invention has particular significance and importance in the environment of supporting motors for driving machinery through belts and pulleys and for supporting the machinery that is driven through belts and pulleys by motors.
In an exemplary but not restrictive environment, a motor is equipped with a spring-loaded variable pitch drive pulley and an adjoining powered piece of machinery is equipped with a driven pulley of a fixed diameter. Changes in the speed of the driven pulley are effected by changes in the center distances between the pulleys. Thus, an increase in the center distance will result in a decrease in the speed of the driven pulley and, on the other hand, a decrease in the center distance will result in an increase in the speed.
In order to effect such changes, the motor is mounted on a movable carriage supported on a fixed base which has a plurality, at least a pair, of parallel cylindrical solid rods that define parallel rails. The carriage is slidable on the rails so that it can move rapidly to achieve the changes in speed. If the motor carriage is to be moved manually on the rails, as is usually the case, it can be appreciated that it is essential that such movement be accomplished with a minimum amount of physical exertion.
Various expedients have been employed in attempts to properly support the carriage so that the carriage and the motor load thereon are evenly transferred to the rails and yet to support the carriage in a way to reduce friction resistance to the sliding of the carriage on the rails.
In one of the earliest attempts, as disclosed in Sloyan U.S. Pat. No. 2,762,663 issued Sept. 11, 1956, the fixed portion of the motor support has parallel rails which are made fast to transverse end cleats and the motor carriage has channel-shaped gliders that encompass portions of the rails and provide a race between the corners thereof and the curved surfaces of the rail with a series of balls being disposed within such defined races. It has been found that the ball bearings, which establish line contacts, are not efficient for many reasons including the fact that grooves are developed in the rails which cause the sliding action to lose efficiency and which also cause the carriage to have a tendency to chatter.
In a subsequent Sloyan U.S. Pat. No. 2,833,597, issued May 6, 1958, the gliders are composed of rectangular tubings which are square in cross section and have an inside dimension materially greater than the outside dimension of the cylindrical rails. C shaped bearing assemblies are provided between the gliders and the rails. Such assembly consists of a metallic bushing which has a freely slidable, non-chattering fit on the rails, a C shaped metallic member, equal in length to the bushing, the external circumference of which makes line contact with three adjacent internal surfaces of the square tube glider, a member of resilient material equal in length to and having a push fit over the bushing and having an external diameter slightly greater than the nominal internal diameter of the C shaped member, so that as the assembly of bushing, resilient member and C shaped member are forced into the glider, that portion of the resilient member not enveloped by the C shaped member but which contacts the internal surface of the remaining wall of the glider becomes slightly distorted due to being somewhat compressed between the bushing and the glider. The result is that the bushing becomes slightly non-concentric with the glider. However, the advantage of the resiliency overshadows the lack of concentricity. The resiliency does much to reduce noise likely to develop between the two metallic parts, the bushing and the rail. A typical example is that any noise developed at the source of an air conditioning system is likely to be telegraphed to every room in a building.
In a subsequent Sloyan U.S. Pat. No. 3,017,226, issued Jan. 16, 1962, the cylindrical rails are formed with a predetermined diameter that is uniform throughout their lengths and the gliders are in the form of square tubes having the inside transverse dimensions thereof substantially the same as the diameters of the rails. Midway of the width of each of the four walls of each glider tube tangential line contact is made at each 90 degree interval on the cylindrical rails. This arrangement is very difficult to fabricate and assemble, considering that it is desired that the tubes for the gliders and that the rails both be ordinary commerical products of a shelf item nature. The manufacture of such arrangement, considering the close tolerances, is extremely difficult and the prevention of friction and chattering cannot be achieved to the desired degree.
Sloyan U.S. Pat. No. 3,586,273, issued June 22, 1971, was intended to avoid this problem. In such patent, bushings, which are externally square are bored to slide freely over cylindrical rodlike rails, then enclosed in square tubular glides in a tight non-rotatable fashion. The rodlike rails extend longitudinally and are fixed at their ends in cleats. The square bushings conform to the internal dimensions of the gliders into the ends of which they are applied as shrunk fits. Each bushing is then reamed to establish a through and through longitudinal bore with sufficient clearance to receive the rails in a freely slidable non-chattering fit throughout the lengths of the bushings. The void existing in the gliders between the bushings provides a reservoir for a lubricant.